This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Many humans in the tropics suffer from schistosomiasis, a disease caused by Schistosoma mansoni. This parasite develops in freshwater snails and emerges as cercariae that infect humans. These snail infections are remarkable: 1) they last long [unreadable]cercariae production can continue for months;2) Every day, thousands of cercariae break through the snail's skin and swim to try and infect humans. Infected snails suffer from regular "wounding from within", exposing them to bacteria and other diseases from the environment. This project investigates which snail and parasite genes are important to maintain parasite infection over such a long time. Shortening the survival of infected snails would reduce how many parasites are released to infect humans. Study of invertebrate immunity (different from human immunology) improves our understanding of general immune function. So-called microarray technology is used to identify snail and parasite genes that are important for successful parasite infection, before and during release of cercariae. Survival and gene expression of S. mansoni-infected snails will be studied after exposure to bacteria or another parasite (Echinostoma paraensei) to test whether cercariae-producing snails have weakened immunity. Genes that appear important will be inactivated (using a method called RNAinterference) to try to reduce survival of S. mansoni-infected snails. The overriding hypothesis is that study of immune function and gene expression in S. mansoni infected snails can provide potential means to reduce the lifespan of these snails to prevent them from releasing parasites that can cause disease in humans.